Dynamic Adaptive Streaming over HTTP (DASH), also known as MPEG-DASH, is an adaptive bitrate streaming technique that enables high quality streaming of media content over the Internet delivered from conventional HTTP web servers - wikipedia 
Unlike HLS, HDS, and Smooth Streaming, DASH is codec-agnostic, which means it can use content encoded with any coding format like H.265, H.264, VP9 etc.
Similar to Apple's HTTP Live Streaming (HLS) solution, MPEG-DASH works by breaking the content into a sequence of small HTTP-based file segments, each segment containing a short interval of playback time of content that is potentially many hours in duration, such as a movie or the live broadcast of a sports event.
The content is made available at a variety of different bit rates, i.e., alternative segments encoded at different bit rates covering aligned short intervals of playback time.
While the content is being played back by an MPEG-DASH client, the client automatically selects from the alternatives the next segment to download and play based on current network conditions.
The client selects the segment with the highest bit rate possible that can be downloaded in time for playback without causing stalls or re-buffering events in the playback.
Thus, an MPEG-DASH client can seamlessly adapt to changing network conditions and provide high quality playback with fewer stalls or re-buffering events.
dash.js is an initiative of the DASH Industry Forum to establish a production quality framework for building video and audio players that play back MPEG-DASH content using client-side JavaScript libraries leveraging the Media Source Extensions API set as defined by the W3C.